1. Field of the Invention
The present invention relates to a radiation detection system for use in diagnoses in a hospital, and a radiation imaging apparatus appropriate as an industrial non-destructive inspection apparatus. In this specification, electromagnetic waves such as X-rays, γ-rays, etc., as well as particulate beams such as α-rays and β-rays, are included in “radiation”.
2. Description of the Related Art
With the progress of recent thin film semiconductor processing technology for radiography, apparatuses have been developed for radiographing an X-ray image using a semiconductor sensor. These X-ray detectors can be produced in a relatively flat structure, and are referred to as a flat panel X-ray detector (“flat panel detector”, or “FPD”). The FPD can be an indirect FPD or a direct FPD. The indirect FPD converts X-rays into visible light through a phosphor, and detects the light using an amorphous optoelectronic conversion element and a switch element. The direct FPD does not use a phosphor, but uses amorphous selenium and the like, converts X-rays directly into electrons, and detects them using an amorphous silicon switch element (TFT).
Presently, an image intensifier (I. I.) has become widespread as a common detector for fluoroscopic radiography. The I. I. converts X-rays into visible light by a scintillator, then converts the optoelectronically intensified secondary electrons into visible light again, thereby obtaining an image by a CCD camera. Generally, since the I. I. has high sensitivity, it has been used for a patient to reduce the dosage of exposure to radiation when relatively long time fluoroscopic radiography is required in performing, for example, fluoroscopic radiographing for gastric surgery, surgery on the heart or brain, etc., while inserting a catheter into a vein, and the like.
On the other hand, since a system using the FPDs can momentarily convert an X-ray image into digital data, it has become widespread as a radiographing apparatus capable of performing fluoroscopic radiographing. Although the I. I. has the advantage of high X-ray sensitivity, it also has some problems of, for example, halation at high dosage of exposure to radiation because of a narrow dynamic range, distortion of surrounding images by an electronic lens, poor durability, a heavy device, etc.
To overcome the above-mentioned problems, a new fluoroscopic radiographing detector as a new replacement for the I. I. can be an FPD having a wide dynamic range, less image distortion, and less degradation. A mobile X-ray imaging apparatus using such an FPD is disclosed in Japanese Patent Application Laid-Open No. 2005-000470.
Additionally, Japanese Patent Application Laid-Open No. 11-009579 discloses an X-ray imaging apparatus that has a mechanism of connecting to and disconnecting from an X-ray detection unit for a C arm, and can easily exchange various flat panel detectors having different capabilities and specifications in radiograph size, resolution, etc.